Actuators made of polymers have properties of being light-weighted and flexible as well as inducing no operation noises, and have been expected to be devices of mechanisms for operating artificial muscles or micro devices. Among them, devices adapted to electrochemically expand and contract using conductive polymers such as polypyrrole or polyaniline as driving materials possibly generate energy larger than those by muscles of biological bodies, and have been suggested as polymer actuator devices capable of operating as practical devices. Further, there have been expectations for devices as actuators having larger generation capacity, which employ, as driving materials, conductive polymer materials containing a carbon-based material dispersed therein, such as conductive polymer materials containing carbon nanotubes dispersed therein.
An actuator made of a conductive polymer is operated as follows. By applying a voltage or a current to conductive polymer layers therein to dope the conductive polymer layers with ions from an electrolyte or undope ions from the conductive polymer layers, the conductive polymer layers are expanded or contracted so that the device is driven to be strained.
Further, the electrolyte expansion/contraction mechanism utilizes expansion and contraction induced by electrochemical oxidation reactions and reduction reactions at the time of doping and undoping of the conductive polymer layers. These expansion/contraction phenomena are considered to be caused, along with electrochemical reactions, by the change of the conformation of polymer chains in the conductive polymer, by the expansion and contraction of the conductive polymer layers due to the entrance and exit of ions having a larger volume into and from the conductive polymer layers, or by electrostatic repulsions induced by electric charges of the same type induced in polymer chains.
As an exemplary polymer actuator, it is possible to conceive an actuator having a structure which includes conductive polymer films placed in an electrolytic solution bath for driving the same. Further, as an actuator having a structure different therefrom, there is an actuator disclosed in Patent Document 1. This structure enables placing an active member layer and a counter electrode close to each other using a flexible electrolyte, thereby increasing the effective cross-sectional area of the active member layer which contributes to drive. In this case, the portion which contributes to drive is defined as the active member layer.
FIG. 17A and FIG. 17B are a plan view and a cross-sectional view of a polymer actuator described in Patent Document 1.
The actuator illustrated in FIG. 17A and FIG. 17B includes an active member layer 103 made of a conductive polymer having a rectangular-parallelepiped plate shape and being of a flat-surface thin type, and a flexible electrode 101a made of a metal such as a stainless steel which is provided to be embedded in a substantially-center portion of the active member layer 103 in the thickness direction, wherein the active member layer 103 and the flexible electrode 101a constitute a first electrode layer 101. Second electrode layers 102 having a rectangular plate shape which are made of a metal such as an aluminum foil are placed in the opposite sides with respect to the first electrode layer 101 in the thickness direction, so as to be opposed to and spaced apart from the first electrode layer 101. Further, electrolyte layers 104a are formed so as to contact with the second electrode layers 102 and the active member layer 103 having conductivity. In the above structure, by applying a voltage between the first electrode layer 101 and the second electrode layers 102, the conductive active member layer 103 is caused to expand or contract, thereby causing the actuator to operate. In this case, the electrolyte layers 104a are formed from electrolytes having a value of elasticity modulus of 3 kN/m2 or less, in order not to obstruct the expanding and contracting operations of the active member layer 103.
The actuator is provided, at the respective end portions in the longitudinal direction, with force acting portions 108 as rectangular plate-shaped extending portions from the first electrode layer 101, and is further provided with holes in the pattern-formation sides opposite from the end edges of the force acting portions 108. Pins 107a of loading hooks 107 are inserted in these holes, so that acting forces 108a can certainly act on the loading hooks 107. By applying a voltage between the first electrode layer 101 and the second electrode layers 102 from a power supply 120 using a switch 121, the active member layer 103 is caused to expand or contract in the longitudinal direction, in other words, in the direction of expansion and contraction (namely, the direction of the driving force output from the actuator) 106, thereby causing the actuator to operate.
Further, in order to enclose the electrolyte layers 104 contacting with the active member layer 103 between both the electrode layers 101 and 102, the entire portion other than the force active portions 108 is covered with a flexible sealing member 109 which does not obstruct the movements of the force acting portions 108. With the sealing member 109, it is possible to maintain strength for preventing the electrolyte layers 104 from being moistened or from being damaged by external forces and the like. A flexible silicon-based rubber having a longitudinal elasticity modulus of about 100 kN/m2 is employed as the sealing member 109, thereby achieving a structure which further prevents the expansion and contraction of the active member layer 103 from being obstructed.
Further, there is provided the following structure for preventing the layers from separating from one another, when large strains are induced for performing operations.
Holding members 105a are inserted between the active member layer 103 and the second electrode layers 102, and the second electrode layer 102, the first electrolyte layer 104a, the active member layer 103, the first electrolyte layer 104a, and the second electrode layer 102 are pinched in a lateral direction from the outside by substantially-U shaped clips 105b. The holding members 105a have a function of maintaining the thickness between the active member layer 103 and the second electrode layers 102. This actuator is of a flat-surface thin type, and the clips 105b are each formed from an insulating plastic plate shaped into a clip shape, for example, and are adapted to pinch this actuator to press the holding members 105a. 
Further, Patent Document 2 discloses a structure which includes a lubricating electrolyte layer between a conductive film and an electrolyte plate for enabling the conductive film and the electrolyte plate to slide with respect to each other due to the lubricating property exhibited by the material for the lubricating electrolyte layer itself.
Further, Patent Document 3 discloses a structure which includes an actuator film and a counter electrode which are placed in an electrolyte solution and, further, is adapted to apply a voltage between the actuator film and the counter electrode for expanding and contracting the actuator film.